In the prior art it is known that underground objects, for example underground structures such as those made of steel-reinforced concrete, can suffer damage, for example if they are exposed to moisture in particular from chemical elements introduced into the underground object with the moisture. Thus for example damage can occur when the moisture penetrates into the underground structure and a steel reinforcement present therein begins to corrode as a result, in particular when salts with chloride ions, are introduced into these underground structures by the moisture. This can occur for example from exposure to deicing salt in winter, in particular in the case of roadways that qualify as underground structures.
In the context of the invention, underground objects may be, in addition to the roadways referred to here as an example, in particular bridge structures forming a roadway, as well as other, in particular statically loaded structures, particularly those made of concrete and in particular those made of steel-reinforced concrete or also of other cement-bound materials, in particular hydraulically setting materials.
However, the invention is not limited to underground structures made of steel-reinforced concrete. Also underground structures made purely of metal, for example steel girders or also pure soil, for example below disposal sites, can and should be monitored by a system according to the invention and, if applicable, also protected against damage, for example moisture damage or damage from to chemical contamination.
Previous systems for monitoring and/or for protecting underground objects with regard to damage, such as for example moisture damage, provide for sealing of such an underground object to be carried out, in particular above an underground object, in order to prevent moisture and substances potentially transported therewith from penetrating into these underground objects. Such sealing is sometimes not carried out with the appropriate care or can age in the course of time, leaking as a result, and thus over time allow damage to an underground object.
In the context of the invention damage is regarded not only as damage caused by moisture, but also the ingress of moisture itself, for example from damage in a seal.
Previous systems for monitoring underground objects with regard to damage, such as for example moisture damage, provide for example for mobile devices that travel over the surface of an underground object, for example the concrete surface of an underground structure made of steel-reinforced concrete engaging electrodes with the underground structure and measuring voltage potentials, in order thus to enable corrosion in the steel reinforcement of an underground structure to be traced. Such systems are complex and labor-intensive and can only conduct monitoring on demand, but do not offer a permanent monitoring facility. Furthermore, such systems cannot be used on coated underground objects.
Such systems also have the disadvantage that only damage that has already occurred can be identified, but an incident that will lead to consequential damage, such as for example the appearance of moisture, for example in the event of a damaged seal, cannot be detected before the occurrence of further damage.